An inkjet printer head, one embodiment of liquid-jet head through which liquid droplets are jetted out toward media via the nozzle orifices thereof, has a nozzle plate, and a plurality of fine inkjet orifices through which ink is jetted out are formed in the nozzle plate at fine intervals. If ink adheres to the surface of the nozzle plate, then other ink that is jetted out later may be influenced by the surface tension and the viscosity of the previously-adhering ink to have a curved jetting trajectory. This arises a problem that the ink could not be applied to a predetermined site. Accordingly, the nozzle plate surface has to be subjected to liquid-repelling treatment for protecting it from ink adhesion.
Some methods mentioned below are known as the technique of liquid-repelling treatment. One of the methods is as follows: A nozzle plate at room temperature is dipped in a solution of a liquid-repellent silane coupling agent such as an alkoxysilane solution for tens seconds. In this stage, the temperature of the alkoxysilane is at around room temperature. Next, the dipped nozzle plate is pulled up out of the solution at a rate of about few mm/sec, thus forming a monomolecular film of an alkoxysilane polymer on its surface. The nozzle plate is then dried for one full day at room temperature to vaporize the solvent, thereby obtaining a water-repellent monomolecular film on the metal surface of the nozzle plate through dehydrating polycondensation.
As another example of the methods, a method described in Patent Document 1 can be cited. This method comprises dipping an absorbent in a mixture of a fluorine-containing polymer compound and a compound having a fluorine-substituted hydrocarbon group and a silazane, alkoxysilane or halogenosilane group, then pulling it up out of the solution, and moving the absorbent while pressed against a nozzle plate to effect coating on the nozzle plate. After thus coated, the nozzle plate is thermally dried and cured at 150° C. for 1 hour to thereby form a liquid-repellent film thereon.
As a still other example of the methods, a method described in Patent Document 2 can be cited. This method comprises masking a nozzle plate, at a part thereof not requiring liquid-repellency, with an aluminium mask, and dipping it in a solution mixed with a substance having a plurality of trichlorosilyl groups, for about 30 minutes to thereby form a chlorosilane monomolecular film thereon. Then, the chlorosilane monomolecular film is washed with chloroform and then with water so that it is reacted to form a siloxane monomolecular film. The siloxane monomolecular film is dipped in a solution of a substance having a fluorocarbon group and a chlorosilane group for about 1 hour, whereby a fluorine-containing monomolecular film is formed on the surface of the nozzle head and the thin aluminium film thereon. Next, the thin aluminium film is etched away, and thus a liquid-repellent monomolecular film is formed on the surface of the nozzle head.
Patent Document 1: JP-A 5-116309
Patent Document 2: JP-A 5-116324
The alkoxysilane molecular film reacts with the OH group that terminates the nozzle plate surface and bonds to the nozzle plate. Accordingly, if a large number of OH groups exist on the nozzle plate surface, then alkoxysilane molecules corresponding to the existing OH groups bond to the nozzle plate. In other words, if a larger number of OH groups exist thereon, then the resulting molecular film has a higher density and, as a result, the liquid-repellency of the resulting nozzle plate is higher. However, since the number of OH groups existing on the surface of metal such as stainless steel is smaller than that on the surface of glass or the like, the obtained molecular film formed through polymerization of a silane coupling material on the surface of metal merely had a low density and poor adhesion. Accordingly, there was a problem that the water-repellency of the molecular film is low and that the film could not ensure its water-repellency for a long period of time.
Ink heretofore used in the background art was generally dye-based ink, and its solvent was water. Therefore, a water-repellent molecular film could repel such dye-based ink so long as it has water repellency. Recently, however, pigment-based ink has become used to cope with high-quality prints from digital still cameras, etc. For the solvent for such pigment-based ink, a resin-based dispersant is used. Therefore, molecular films for printer members for such pigment-based ink are required to have both water repellency and oil repellency (hereinafter collectively referred to as “liquid repellency”). However, the molecular films disclosed in Patent Documents 1 and 2 do not have both water repellency and oil repellency, and hence involve a problem that the molecular films are wetted.
Heretofore, the members of liquid-jet devices other than nozzle plates were not treated for ink repellency. The absence of ink-repellency treatment arises the following problem. Ink adheres to no small extent to the members such as cap and wiper that directly contact with ink, and if the members are formed of wettable material, then the ink having adhered thereto may stay thereon as such. When the adhered ink is left as it is, it may thicken to cause staining and operation failure of the members. Especially with respect to wiper members, ink is led through or to various members, such as from wiper body (rubber, elastomer, urethane) to wiper-holding lever (polyoxymethylene (POM)), then to system body (acrylonitrile-butadiene-styrene (ABS)) and to waste absorbent, and is absorbed by these members. Therefore, there is a probability that ink may be hardly led through or to these members. In addition, thickened ink may adhere to a lower part of a carriage on which a head is to be mounted, and it may be transferred onto the head upon operation of the wiper.